Eastern Command was a pre-war formation, one of the four command areas that comprised the Army in India. It covered the north-central, and north-eastern provinces of British India, and several Princely states. It was a Lieutenant General or General’s appointment, with a full staff of personnel at Command Headquarters, which were located at Naini Tai.

It comprised the:

Meerut District (3 Indian Division);
Lucknow District;
Presidency & Assam District.

With the outbreak of war with Japan on 8 December 1941, there were few changes to Eastern Command. As the Japanese Army advanced up through Burma, it was necessary to change the status of the command to an operational command tasked with defending the eastern frontier of India, therefore, it was redesignated as the Eastern Army on 13 April 1942, with its headquarters located at Ranchi.

The Presidency and Assam District was used to form the basis of the new Headquarters, XV Indian Corps, and formed the Assam Division. The Meerut and Lucknow Districts transferred to the newly formed Central Command. On 21 April 1942, the Eastern Army had under command:

Assam Division (Jorhat);
IV Corps: (Ranchi) (Lieutenant General N. M. S. IRWIN);
XV Indian Corps: (Barrackpore) (Lieutenant General Sir Noel BERESFORD-PEIRSE).

The Assam Division was temporary formation created from elements of Headquarters, Presidency and Assam District. A short time later the 1 Indian Infantry Brigade transferred to the command of 23 Indian Division, and the Assam Division disbanded. The XV Indian Corps was newly created from Headquarters, Presidency and Assam District, and had its headquarters based at Calcutta and then Barrackpore.

In August 1942, three new Lines of Communication Areas were formed in the Eastern Army to relieve the operational corps of the responsibility for internal security and other non-operational commitments.

101 Lines of Communication Area – H.Q. Patna then Ranchi;
202 Lines of Communication Area – H.Q. Dimapur;
303 Lines of Communication Area – H.Q. Calcutta;
404 Lines of Communication Area – H.Q. Chittagong.

On 15 October 1943, the process began to split the Headquarters Eastern Army to form the new Headquarters 14 Army and Eastern Command. A new Army Group was created, with the General Officer Commanding-in-Chief of Eastern Army being appointed to command the new 11 Army Group; which was formed in Delhi on 16 October and then moved to Barrackpore.

When the Eastern Army spilt to form 14 Army and Eastern Command on 22 October 1943, 101 Lines of Communication Area and 303 Lines of Communication Area came under Eastern Command; with 202 Lines of Communication Area and 404 Lines of Communication Area coming under command of 14 Army.

With the end of the war, the Eastern Command was reorganised onto a peacetime establishment. The 101 L.o.C. Area became the Bihar and Orissa Area, and the 303 L.o.C. Area became the Bengal and Assam Area.

Central Command was disbanded in September 1946, and two Areas were transferred back to Eastern Command. After September 1946, Eastern Command comprised four Areas:

United Provinces Area (formerly the Lucknow District) – H.Q. Lucknow;
Bihar and Orissa Area – H.Q Dinapore;
Bengal and Assam Area – H.Q. Calcutta;
Delhi and East Punjab Area (replaced the Delhi District) – H.Q. Delhi.

This was the situation when British India partitioned on 15 August 1947, and Eastern Command became part of the new Indian Army. Shortly after partition, the Delhi and East Punjab Area was raised to Command status.